Idiopathic interstitial pneumonia (IIP) is a cryptogenic disease characterized by the fibrosis of lung tissues. It is extremely difficult to predict the onset and progression of this disease.
According to histological classification, idiopathic interstitial pneumonia is classified into several types of disease, such as idiopathic pulmonary fibrosis (IPF) (or also referred to as usual interstitial pneumonia (UIP)) and nonspecific interstitial pneumonia (NSIP). IPF/UIP patients and NSIP patients account for 80% to 90% of all idiopathic interstitial pneumonia patients. NSIP is further classified into fibrotic NSIP and cellular NSIP. At present, there are no effective methods for a medical treatment of idiopathic interstitial pneumonia. Idiopathic interstitial pneumonia has a poor prognosis, and the median survival period of this disease is 2 to 4 years after the diagnosis of the disease. On the other hand, the prognosis of NSIP is better than those of IPF/UIP. Among others, the prognosis of cellular NSIP is much better than that of fibrotic NSIP. Thus, since the prognosis of patients with idiopathic interstitial pneumonia is different depending on the type of the disease, it is important to determine the type of idiopathic interstitial pneumonia in order to predict the prognosis of the patient with this disease.
The diagnosis of idiopathic interstitial pneumonia has been mainly made by radiography, an image diagnosis such as CT, a physiological pulmonary function test, etc. The definitive diagnosis has been made by a histological diagnosis involving the biopsy of lung tissues. However, the diagnostic accuracy of such image diagnosis is not as high as that of the histological diagnosis, and further, the image diagnosis requires high skilled, specialized diagnostic techniques. Furthermore, it is difficult for such image diagnosis to perform a quantitative diagnosis.
Under the aforementioned circumstances, it has been desired to develop a noninvasive diagnosis in addition to such an image diagnosis.
Document 1 describes that allergic disease is examined using the expression level of a periostin gene as an indicator.
Document 2 describes that periostin (osteoblast-specific factor 2) is generated in fibroblasts as a result of response to stimulation with IL-4 or IL-13, and that such periostin may be associated with the pulmonary fibrosis of patients with bronchial asthma.